1. Field of the Invention
The present invention relates generally to chemical laser systems, and more particularly to the use of iodine monochloride and molecular iodine as the iodine source for chemical oxygen iodine laser (COIL) systems.
2. Discussion of the Related Art
The fact that an atom will emit a photon of radiation when one of its electrons drops to a lower energy state has enabled the laser to be employed in a number of military, industrial, and medical applications. The term xe2x80x9claserxe2x80x9d is an acronym for light amplification by stimulated emission of radiation. In its simplest form, a laser consists of a rod of transparent crystal or a tube filled with gas or liquid. A mirror is placed at one end and a half-silvered mirror at the other end. The laser is then xe2x80x9cpumpedxe2x80x9d by adding energy, e.g., by shining another light source into it, by adding electrical energy, or by stimulating a chemical reaction. This process raises electrons in the laser to higher energy states.
During the pumping process, some of the electrons will spontaneously fall back to a lower energy state, emitting photons. The photons that travel toward the sides of the laser are quickly lost, but those traveling along the length of the rod or tube are reflected back by the mirrors. This activity generally occurs in the area commonly referred to as the laser gain region. When these photons strike other excited atoms, they stimulate those atoms to release photons of the exact same energy level (or wavelength), which travel in the same direction as the stimulating photons. The result is an intense, highly focused beam of light escaping through the half-silvered end of the laser. This light beam is generally referred to as a beam of high energy coherent radiation, or more commonly, a laser beam.
Because the photon wavelength is determined by the characteristics of the atoms in the lasing material, laser light is of a single wavelength. Because laser light travels in a tight beam, it can carry a great deal of energy over a great distance without significant loss. With respect to recent developments in laser technology, there has been increased interest in chemical laser systems, especially COIL systems.
The COIL system was initially developed for military applications; however, recent attention has turned to potential industrial uses of COIL systems, such as metal cutting applications.
In a COIL system, chlorine gas reacts with a solution of basic hydrogen peroxide (i.e., H2O2) (usually KOH or NaOH mixed with hydrogen peroxide) to produce a gaseous flow of excited oxygen, also referred to as singlet delta oxygen or singlet molecular oxygen (designated as O2*, O2(1xcex94), as well as by other symbols). This gaseous flow of singlet delta oxygen collides (typically at speeds approaching or even exceeding the speed of sound) with iodine gas molecules (i.e., I2), dissociating them and subsequently exciting the resulting iodine atoms (i.e., I), which lase at 1.315 xcexcm. The major laser byproducts are various salts (e.g., NaCl or KCl) and heat. The small amounts of iodine can be scrubbed from the output.
FIG. 1 illustrates a highly simplified schematic of the intended operation of a conventional COIL system 10. The initial step is to generate the singlet delta oxygen. This is accomplished by providing a source 12 of basic hydrogen peroxide, typically in liquid form, and a source 14 of molecular chlorine, typically in gaseous form. These two materials are then charged or injected into a singlet delta oxygen generator 16 through appropriate manifold/conduit assemblies 18, 20, respectively. The resulting exothermic reaction between the basic hydrogen peroxide liquid and the molecular chlorine gas produces the gaseous singlet delta oxygen, as well as several by-products, such as salt and heat. The heat can be removed by appropriate devices such as a heat exchanger (not shown), and the salt can be removed by appropriate devices such as a scrubber (not shown). The skilled artisan will appreciate that various well-known auxiliary components of the conventional COIL system 10 have been omitted for ease of illustration.
Once the gaseous singlet delta oxygen is generated, it is then charged or injected in flow form into a mixing nozzle 22 at the appropriate time. The mixing nozzle 22 has a throat portion 23 which generally divides the mixing nozzle 22 into a subsonic zone 24 and a supersonic zone 26; that is, the flow of gaseous singlet delta oxygen is subsonic in one portion of the mixing nozzle 22 and supersonic at the other portion of the mixing nozzle 22. The mixing of reactants is typically done in the subsonic zone 24.
A molecular iodine generator 28 is in communication with the mixing nozzle 22 by an appropriate manifold/conduit assembly 30. At the appropriate time, gaseous molecular iodine is then charged or injected into the mixing nozzle 22 in such a manner so as to let it xe2x80x9cpoolxe2x80x9d before completely mixing with the singlet delta oxygen gas flowing from the singlet delta oxygen generator 16. The slight delay in mixing due to this xe2x80x9cpoolingxe2x80x9d permits the singlet delta oxygen to dissociate only some of the molecular iodine on the edge of the xe2x80x9cpoolxe2x80x9d and thus initiate the chain reaction dissociation of molecular iodine by the product atomic iodine. However, in this xe2x80x9cpoolingxe2x80x9d process, significant singlet delta oxygen is nonetheless lost due to excess reaction with molecular oxygen or deactivation with water, iodine, liquid or solid surfaces, or other loss mechanisms.
The primary reactions taking place in connection with the conventional COIL system 10 are as follows:
(1) I2+O2*xe2x86x92I2*+O2. That is, a mole of molecular iodine reacts with a mole of singlet delta oxygen to produce a mole of excited molecular iodine and a mole of molecular oxygen.
(2) I2*+O2*xe2x86x922I+O2. That is, a mole of excited molecular iodine reacts with a mole of singlet delta oxygen to produce a two moles of atomic iodine and a mole of molecular oxygen.
(3) I+O2*xe2x86x92I*+O2. That is, a mole of atomic iodine reacts with a mole of singlet delta oxygen to produce a mole of excited atomic iodine and a mole of molecular oxygen.
(4) I*xe2x86x92I+hxcexd. That is, a mole of excited atomic iodine releases a mole equivalent of photons (hxcexd), thus producing a mole of atomic iodine.
The singlet delta oxygen gas flow initially contacts the gaseous molecular iodine xe2x80x9cpoolxe2x80x9d at subsonic speed; however, the singlet delta oxygen gas flow is quickly brought up to near supersonic or even supersonic speed (via appropriate devices such as a venturi) and is expelled out through the mixing nozzle 22 into the area known as the laser gain region 32 of the laser cavity 33. It is in this area where the excited atomic iodine releases its photon. The released photon is then reflected many times between a set of mirrors 34, the first mirror 36 being fully reflective, the second mirror 38 being partially reflective. The reflected photons eventually form a laser beam 40, which is transmitted through the partially reflective mirror 38 at a wavelength of 1.315 xcexcm. Any remaining chemical species are removed from the laser gain region 32 by a combination of exhaust assemblies (not shown) and scrubber assemblies (not shown) in order to avoid contamination of the laser""s mirrors 34.
COIL systems have long been known to output less laser power than is theoretically available from the singlet delta oxygen leaving the generator. There are a number of proposed kinetic explanations for this, as well as several proposed or alternative approaches to increasing the output laser power. The advantages of enhanced power extraction from a given generator are substantial in the weight, volume and complexity of nearly all proposed applications of COIL systems.
Iodine monochloride has been suggested as a replacement for molecular iodine for COIL systems. It was found that under certain circumstances, conventional COIL systems were suffering from condensation of molecular iodine particles that would seriously degrade the laser""s operation. This problem was due to the relatively low vapor pressure of molecular iodine. Therefore, it was suggested to employ iodine monochloride which has a vapor pressure of 5300 pascals (Pa) at 300xc2x0 K, as opposed to molecular iodine which has a vapor pressure of 63 Pa at 300xc2x0 K. A complete description of this technology can be found in U.S. Pat. No. 4,653,062 to Davis et al. issued Mar. 24, 1987, the entire specification being expressly incorporated herein by reference. Despite the potentially attractive features of rapid iodine monochloride dissociation kinetics, it was found that far greater quantities of singlet delta oxygen were lost than in systems simply employing molecular iodine alone. These losses were so great that further work with iodine monochloride was essentially abandoned.
Therefore, there is a need to develop an iodine source for a COIL system that will possess the required dissociation kinetics in order to efficiently utilize all or most of the available singlet delta oxygen to maximize production of excited atomic iodine and subsequent photon release.
The present invention provides an iodine source for a COIL system, wherein the iodine source comprises both molecular iodine and iodine monochloride. The molecular iodine and the iodine monochloride are combined together, either prior to or after being charged into the mixing nozzle, in order to initiate a chain reaction between the two that will rapidly make available a large amount of atomic iodine to react with the singlet delta oxygen.
In accordance with the general teachings of the present invention, a chemical oxygen iodine laser system for producing a beam of high energy coherent radiation comprises a singlet delta oxygen generator for producing a gaseous flow of singlet delta oxygen; a molecular iodine generator for producing a gaseous flow of molecular iodine; an iodine monochloride generator for producing a gaseous flow of iodine monochloride; and a mixing nozzle for receiving gaseous reactants and discharging these reactants in a mixing flow.
In accordance with the general teachings of the present invention, a method for producing a beam of high energy coherent radiation comprises the steps of: providing a mixing nozzle for receiving gaseous reactants and discharging these reactants in a mixing flow; providing a gaseous flow of singlet molecular oxygen into the mixing nozzle; providing a gaseous flow of iodine monochloride into the mixing nozzle, the iodine monochloride reacting with the singlet molecular oxygen and thereby dissociating into atomic iodine and atomic chlorine; and providing a gaseous flow of molecular iodine into the mixing nozzle, the molecular iodine reacting with the atomic iodine to produce additional atomic iodine.
In accordance with the general teachings of the present invention, an alternative method for producing a beam of high energy coherent radiation comprises the steps of: providing a mixing nozzle for receiving gaseous reactants and discharging these reactants in a mixing flow; providing a gaseous flow of singlet molecular oxygen into the mixing nozzle; providing an iodine monochloride dissociation assembly; providing a gaseous flow of iodine monochloride into the mixing nozzle, wherein the iodine monochloride is dissociated into atomic iodine and atomic chlorine by the iodine monochloride dissociation assembly prior to entering into the mixing nozzle; and providing a gaseous flow of molecular iodine into the mixing nozzle, the molecular iodine reacting with the atomic iodine to produce additional atomic iodine.
In accordance with the general teachings of the present invention, a second alternative method for producing a beam of high energy coherent radiation comprises the steps of: providing a mixing nozzle for receiving gaseous reactants and discharging these reactants in a mixing flow; providing a gaseous flow of singlet molecular oxygen into the mixing nozzle; providing a gaseous flow of molecular iodine into the mixing nozzle; providing an iodine monochloride dissociation assembly; and providing a gaseous flow of iodine monochloride into the gaseous flow of molecular iodine, wherein the iodine monochloride is dissociated into atomic iodine and atomic chlorine by the iodine monochloride dissociation assembly prior to entering into the gaseous flow of molecular iodine molecular, the atomic iodine reacting with the molecular iodine to produce additional atomic iodine.
Additional objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.